Process for purification of manganese alloys

ABSTRACT

Metallic materials, such as manganese containing materials, which contain a residual impurity, such as lead are purified by subjecting a melt of the material to a gaseous blow with a carrier gas, which is generally non-reactive with melt material and which removes the impurity through evaporation.

[ Dec. 16, 1975 United States Patent [191 Keyser et a1.

[ PROCESS FOR PURIFICATION OF Bampfydle Strauss....................

MANGANESE ALLOYS [75] Inventors: Naaman H. Keyser, l-linsdale;

2,871,008 1/1959 Spirem... 3,060,015 10/1962 Spolders.,...,........... 3,369,887 3,484,232

2/1968 Keyser.......1............ 12/1969 Karinth 22 Filed; Dec, 4, 1974 FOREIGN PATENTS OR APPLICATIONS 21 Appl. No.: 529,682

852,142 10/1960 United Kingdom.....................75/59 Related US. Application Data [63] Continuationin-part of Ser. No. 317,044, Dec. 20,

Primary Examiner-M. J. Andrews Attorney, Agent, or FirmTeare, Teare & Sammon 1972, abandoned, which is a continuation of Ser. No. 46,010, June 15, 1970, abandoned.

T C A R T S B A U 5 3 B 1J7... 0 8 N 7 8 2 B 5 5 7 7 "5 C M U H 5 1 Metallic materials, such as manganese containing ma [51] Int. C22C 35/00 terials, which contain a residual impurity, such as lead are purified by subjecting a melt of the material to a l M 1 M @1 ,5 $3 ,1 O 7 00E 3 9 2 H00 500 7 .7 "7 m3 m6 m l c r an &/ 5 f7 0 d l e i F 1. oo 5 .1

gaseous blow with a carrier gas, which is generally non-reactive with melt material and which removes the impurity through evaporation.

[56] References Cited UNITED STATES PATENTS 1,019,965 3/1912 75/59 12 Claims, 2 Drawing Figures Patent Dec. 16, 1975 INVENTORS NAAMAN lH. KEYSER AKGUN MERTDOGAN ATTORNEYS PROCESS FOR PURIFICATION OF MANGANESE ALLOYS CROSS REFERENCE TO PRIOR APPLICATION This application is a continuation-in-part of application Ser. No. 317,044 filed Dec. 20, 1972, now abandoned, which was a continuation of application Ser. No. 46,010 filed June 15, 1970 now abandoned.

BACKGROUND OF THE INVENTION The invention relates generally to the purification of metals and metal alloys, and more specifically to the removal of impurities from manganese-containing materials such as ferromanganese alloys, silicomanganese alloys, and manganesesilicon ferro-alloys. In particular, the invention is concerned with the production of high grade alloys, such as, for example, standard silicomanganese containing at least 65% manganese and up to 30% silicon. Such silicomanganese is widely used in the production of steel, and in the production of low or medium carbon ferromanganese.

Manganese alloys, such as ferromanganese and silicomanganese, or the like, are conventionally produced from manganese ore. Such ore usually contains some residual impurity, such as lead, zinc or arsenic. Unless such impurity can be removed, or reduced, to a tolerable amount, the alloy made from such ore is of an inferior quality, or is, for all practical purposes, useless for many steel-making operations.

Where conventional techniques are used for alloying, it has been previously necessary to select and utilize only ores having less than a maximum residual impurity content. This maximum amount was approximately the same as the maximum amount of impurity tolerable in the alloy made from such ore since the impurity content of the alloy was generally proportional to the impurity level of the ore itself.

For example, commercial silicomanganese alloys are conventionally produced in an electric arc furnace by either (1) simultaneous reduction of manganese ore having less than the predetermined maximum impurity level and quartzite, or (2) by reduction of silicon from qualtzite with the addition to the charge of carbon ferromanganese having less than the predetermined maximum impurity level, or (3) by melting of ferrosilicon with ferromanganese having less than the predetermined maximum impurity level. The first method has been the usual method for producing standard silicomanganese.

In addition, ferromanganese alloys of high purity are also produced by conventional methods, utilizing this preselection of manganese ore of the necessary low residual impurity content.

Because of the requirement of low residual impurity ore as the starting point of the process, time has been heretofore lost in selecting ore of the desired grade. In addition, where the preselection technique was used, the supply of high grade ore was necessarily limited by the low residual impurity requirement.

Heretofore, it has also been known to remove gaseous impurities by subjecting the unrefined melt to a Still further, gaseous blows have been utilized heretofore to effect a more efficient separation of an impurity where the impurity is solidifying out of a melt as it cools. This procedure assumes of course that the impurity will precipitate or solidify out of a melt, a contingency which does not always occur.

The following are illustrative of prior methods of removing impurities:

1. US. Pat. No. 2,866,701 to Strauss, issued Dec. 30, 1958 2. US. Pat. No. 3,060,015 to Spolders et al., issued Oct. 23, 1962 3. US. Pat. No. 3,288,594 to Smith, issued Nov. 29, 1966 4. US. Pat. No. 3,326,672 to Wormer, issued June 20, 1967 5. US. Pat. No. 3,380,509 to Hentrich et al., issued Apr. 30, 1968 6. US. Pat. No. 3,468,657 to Pihlblad et al., issued Sept. 23, .1969

SUMMARY OF THE INVENTION The present invention provides a novel method for producing metallic materials of reduced impurity level, whereby a melt of the material can be made by initially following conventional methods without regard for the impurity level of the raw material. The conventionally produced melt is then treated in accordance with the present invention to produce an end product which is below the maximum tolerable level of impurities, which in the case of lead would be below 0.01 percent by weight, and preferably, not in. excess of 0.006% by weight.

For example, the first step may be the production of a melt of a manganese-containing material in an electric furnace by conventional means. Such a melt may have, for example, a manganese content in the range of approximately 60% to 72% by weight, a silicon content in the range of approximately 2.4% to 30% by weight and a lead content of 0.20 percent and greater. Such melt may then be separated from the slag by being tapped into a ladle in the conventional manner. In accordance with the present invention, a graphite lance is then inserted into the molten material in the ladle. A carrier gas, such as chorine, carbon monoxide, air, natural gas or nitrogen is then blown into the melt under pressure, causing reduction of the impurity level to a predetermined level. The purified material of the desired high degree of purity may then be poured from the ladle and case into molds.

By the foregoing invention, the source of supply of manganese are useable for low impurity alloy production is increased; preparation and preselection of'manganese ore, or other raw materials, with the desired level of impurities is eliminated; and alloys which might otherwise have been of an inferiorgrade, due to errors in preselection, can be salvaged.

In addition, the foregoing objects are accomplished without the need for expensive and complex equipment, exacting control of processing conditions, or

. additionalrefining steps.

partial vacuum. Such techniques, however, assume the existence of the impurity as a gas which is not always the case. In addition, the high operating temperatures required to maintain the molten state of the melt make the vacuum equipment expensive.

BRIEF DESCRIPTION OF DRAWINGS FIG. .2 is a 'sid'e'elevation view, partially in vertical section, of the purified melt being removed from the ladle by pouring. I

' DESCRIPTION or THE PREFERRED EMBODIMENTS I In accordance with the present invention, a molten metallic material containing at least one molten impurity, such as a molten-manganese-containing material with a lead impurity or the like, is produced by suitable means known in the art, such as by smelting, and is poured in the molten state into a suitable container means, such as a ladle 10, as shown in FIG. 1. The impure input melt 8 provided thereby is then subjected to a gaeous blow with a carrier gas 22 such as by means of a graphite lance 20. After a predetermined amount of such gas 22 has passed through the melt 8, the gaseous blow is terminated and the purified output melt 8', having a reduced impurity level, is poured from the ladle 10 as shown in FIG. 2, for subsequent use.

While the present invention may be susceptible to use in refining many metals, and metal alloys, it is particularly suited for removing molten impurities from metallic, manganese materials. More specifically, the present invention effectively reduces the residual lead impurity content of 'silico-manganese and manganesesilicon ferro-alloys, such as manganese silicide, standard ferro-manganese, manganese silicide of M55 grade, low carbon ferromanganese and massive manganese. The maximum lead impurity content in the input melt 8 of such silico-manganese and manganese-silicon ferro-alloys is limited only by the maximum amount of lead which is soluble or held in suspension in the particular input melt 8 at the temperature and pressure of the melt during the gaseous blow. In other words, the method of the present invention will tolerate a maximum input impurity level equal to the maximum amount of impurity which is soluble or suspended in the input melt 8 during the gaseous blow. For example, thelead content may be in a range of 0.30 to 1.40%, and possibly greater, by weight of the melt which would generally be the lead content of certain known low grade ores. Generally, the input melt of manganesecontaining material comprises an alloy of manganese including a manganese content in the range from approximately 60% by weight to approximately 72% by weight, a silicon content in the range from approximately 2.4% by weight to approximately by weight, and a residual lead impurity content up to and including the above described maximum. Ironmay also be present, such as an iron content of about 12% by weight. Preferably, the input melt comprises a manganese silicide alloy, a standard ferromanganese alloy, or a manganese silicide alloy'of'M55 grade. The first mentioned manganese silicide alloy preferably has a manganesec'ontent of approximately 60% by weight, a silicon content of approximately 30% by weight and a residual lead impurity content within the aforementioned range. The aforementioned standard ferromanganese preferably has a manganese content of approximately 72% by weight, a silicon content of approximately 2.4% by weight, an iron content of approximately 12% by weight and a residual lead impurity content within the aforementioned range. The M55 grade alloy of manganese silicide preferably has 'a manganese content of approximately 66% by weight, 'a silicon content of approximately 18% by Weight and a residual lead impurity content within the aforementioned range. Instead of the foregoing silico-manganese and manganese-silicon ferroalloys, the input melt 8 may comprise low carbon ferromanganese or massive manganese.

While the present invention is particularly suited for the removal of a lead impurity from manganese-containing materials, zinc or arsenic residual impurities in such manganese containing materials may also be susceptible to removal by the present invention.

Preferably, the environmental pressure to which the input melt 8 is subjected prior to and during the gaseous blow is ambient or atmospheric pressure. The temperature of the input melt 8 at the commencement of the gaseous blow should be sufficiently greater than the melting temperature of both the residual impurity (such as lead) and the materials to be retained in the melt 8 (such as silicon and manganese) so as to ensure proper fluidity of the melt 8 during the gaseous blow. However, it is preferred that the melt temperature be below the boiling temperature of the residual impurity, such as lead, to minimize losses of the materials (such as manganese and silicon) which are to be retained in the melt 8. Accordingly, where the input melt 8 comprises a manganese-containing material with residual lead impurity the melt temperature should be in the range between approximately 2500 F and approximately 2800 F atthe commencement of the gaseous blow.

More particularly, the carrier gas 22 should be of a type which is generally non-reactive with the materials forming the melt, such that at least a major portion will pass by bubbling, entirely through the melt, and evaporate from the melt, without reacting with or otherwise being consumed in the melt. For example, in a method wherein the melt materials are previously set forth, a carrier gas of free oxygen or containing a sizeable portion of free oxygen would combine with the materials of the melt to form solid or liquid products or would be dissolved in the melt to such an extent that the gas would not pass through the melt, or at least only to a limited extent, unless the gas is blown at pressures and quantities in excess of those required for non-reactive gases, and thus, would contribute greatly to the expense of the purification process.

Those gases which have been found to be effective as a carrier gas 22 in removing the molten impurity from the liquid phase of the input melt 8 which comprises a' manganesecontaining material and the impurity comprises lead are:

a. chlorine, and

b. nitrogen I Preferably, a predetermined amount of such carrier gas is blown into the input melt 8 by an immersed conduit means, such as a graphite lance 20. The amount of gas is determined by blowing the gas at a predetermined rate for a predetermined time so as to reduce the impurity content to the desired level. This level may be determined by test samples taken from the melt. In general, a rate of gas flow per ton of melt between about 60 cubic feet per hour and about 1,040 cubic feet ,per hour may be used. Also, a time duration between about 45 minutes and about one hour may be used. Where the residual impurity is lead, the flow rate per ton of melt for chlorine may be between approximately 60 cubic feet per hour and approximately 890 cu. ft. per hour; the flow rate per ton of melt for nitrogen may be between approximately 260 cubic feet per hour and approximately 1040 cubic feet per hour; and the flow rate per ton of melt for air may be about 830 cubic feet per hour. Preferably, chlorine is blown at a rate of about 300 cubic feet per hour per ton for 45 minutes; nitrogen is blown at a rate of about 450 cubic feet per hour per ton for 60 minutes; and air is blown at a rate of about 830 cubic feet per hour per ton for about 60 minutes.

The following specific examples illustrate the application of the present invention to the removal of a residual lead impurity from silico-manganese alloys and manganese-silicon ferro-alloys of high lead content by the use of chlorine, nitrogen and air, respectively.

EXAMPLE I A heat of 200 pounds of silicomanganese alloy assaying by weight 59.65 percent manganese, 30.80 percent silicon, 0002-0003 percent lead was melted in a magnesia-lined, 300-pound capacity induction furnace. The lead content of the alloy was upgraded by adding 1.0 pounds of metallic lead into the alloy during the melting period. The alloy was superheated to a temperature of approximately 2700 F. V

Chlorine gas was introduced into the melt through a graphite lance at the rate of about 11.4 pounds per hour or about 62 cubic feet per hour for a period of 45 minutes. Capillary samples of the melt were obtained throughout the chlorination process at 5 or minute intervals, and the samples were assayed by weight as follows:

Minute Interval Percent Lead A heat of 200 pounds of silicomanganese alloy assaying by weight 59.65 percent manganese, 30.80 percent silicon, 0002-0003 percent lead was melted in a magnesia-lined, 300-pound capacity induction furnace. The lead content of the alloy was upgraded by adding 1.0 pound of metallic lead into the alloy during the melting period. The alloy was superheated to a temperature of approximately 2700 F.

Nitrogen gas was introduced into the melt through a graphite lance at the rate of about 6.0 pounds per hour or about 83 cubic feet per hour for a period of 50 minutes. Capillary samples of the melt were obtained throughout the nitrogen treatment process at 5 or 10 minute intervals and the samples were assayed by weight as follows:

Minute Intervals Percent Lead EXAMPLE III A heat of 200 pounds of silicomanganese alloy assaying by weight about 60 percent manganese and 30 percent silicon was melted in a magnesia-lined, 300- pound capacity induction furnace. The lead content of the alloy was upgraded by adding 1.0 pound of metallic lead into the alloy during the melting period. The alloy was superheated to a temperature of about 2700 F.

Air was injected into the melt through a graphite lance at the rate of about 6.3 pounds per hour, and was continued for 60 minutes. Capillary samples of the melt were obtained throughout the air treatment process at 5- or 10-minute intervals, and the samples were assayed by weight as follows:

Minute Intervals Percent Lead A heat of 300 pounds of standard ferromanganese having, by weight, a 78,30 percent manganese, 2.38 percent silicon, 12.01 percent iron and 6.4 percent carbon content was melted in a manganese-lined 500- pound capacity induction furnace. The lead content of the alloy was upgraded by adding 1.5 pounds of metallic lead into the alloy during the melting period. The alloy was superheated to a temperature of approximately 2800 F.

Nitrogen gas was introduced into the melt through a graphite lance at the rate of about 7.5 pounds per hour for a period of 60 minutes. Capillary samples of the melt were obtained throughout the nitrogen treatment process at IO-minute intervals, and the samples were assayed by weight as follows:

Minute Intervals Percent Lead The foregoing examples illustrate that the invention produces an improved, purified output melt having a reduced residual impurity level. More particularly, the method of the present invention produces a melt of manganese-containing material with a reduced lead impurity level, such as less than 0.12 percent by weight, and more particularly, to approximately 0.006 percent or less by weight. A compilation of the quantities and flow ratio of the carrier gases used in the examples per ton of melt would be as shown in the following chart:

Total Gas Flow Rate, Lead, by Weight Carrier Blown CF/ Input Output Example Gas CF/Ton Ton Melt Melt l Chlorine 465 620 0.057 0.005

11 Nitrogen 691 830 0.065 0.006 Ill Air 830 830 0.057 0.006 IV Nitrogen 667 667 0.058 0.012

As can be seen, chlorine gase was effective in lowering the lead content of the melt to 0.005% by weight when blown in the amount of 465 cubic feet per ton of melt and at a rate of 65 to 620 cubic feet per hour per ton for a period of 45 minutes. The nitrogen gas reduced to lead content to 0.006% by weight when a quantity of 691 cubic feet per ton was blown for 50 minutes at a rate of 830 cubic feet per hour per ton, whereas, quantities of less than 691 cubic feet per ton or at rates less than 830 cubic feet per hour per ton did not lower the lead content of the melt to 0.006 percent by weight over a period of 60 minutes. When air was injected in the quantity of 830 cubic feet per ton at a rate of 830 cubic feet per hour per ton for 60 minutes the lead content of the melt was reduced to 0.006% by weight.

The present invention provides a simple and economical means of removing residual impurities from metallic manganesecontaining material. The present invention also provides an effective means for upgrading or salvaging alloys which would ordinarily have unacceptable impurity levels, such as in excess of 0.10 percent, and more particularly in a range of 0.30 to 1.40% by weight, thereby permitting the use of more inexpensive ores and other raw materials. In addition, the carrier gas used is readily obtainable and is relatively inexpensive to use.

It is believed that the removal of the impurity from the melt occurs primarily as an evaporation phenomenon. Since the impurity, as it exists in the melt, is below its vaporization or boiling point, it is believed that the carrier gas passing through the melt creates a concentration differential between the gas phase of the carrier gas and the liquid phase of the melt. The impurity passes from the liquid phase (of greater impurity concentration) to the gas phase (of less impurity concentration) and exists from the melt, leaving the other melt materials, such as manganese and silicon, in the ladle. Accordingly, the carrier gas need not react substantially with the residual impurity. In the case of a residual lead impurity, this means that the majority of the lead should be removed in its elemental state.

Consequently, the carrier gas used in the gasous blow should be a gas which removes the residual impurity from the liquid phase of the input melt without substantial removal of the melt material which is to be retained (such as manganese and silicon). Such a gas should produce a change in the percent by weight values for manganese and silicon between the input melt and the output melt which is less than about 3% by weight.

We claim:

1. A method for producing ferro-alloys from a manganese containing ore for use in steel production, the steps comprising,

providing an input melt from manganese containing ore with said input melt comprising a manganesecontaining material selected from a group consisting of:

a. a silico-manganese ferro-alloys,

b. a manganese-silicon ferro-alloy, c. a low carbon ferro-manganese, and d. a massive manganese, said input melt containing a molten impurity content selected from the group consisting of: a. lead, b. arsenic, and c. zinc providing the impurity content in an amount in excess of 0.01 by weight, providing a carrier gas of the type which does not generally react or combine with the materials of said input melt or said impurity content at a temperature above the melting temperature of said impurity content, but below the vaporization temperature thereof, blowing said carrier gas entirely through said input melt so that it will pass out of the input melt, maintaining the temperature of said input melt above the melting temperature of said impurity content while blowing said carrier gas therethrough and, separating said impurity content from said input melt by said carrier gas to cause said impurity content to be evaporated and removed as a gaseous vapor in substantially its elemental state along with said carrier gas as it passes out of said input melt to reduce the impurity content in said melt to an amount less than 0.01% by weight. 2. A method in accordance with claim 1, including blowing a carrier gas of the type having a minor percentage by weight of free oxygen. 3. A method in accordance with claim 1, including blowing a carrier gas having less then 22% by volume or 24% by weight of free oxygen. 4. A method in accordance with claim 1, wherein said carrier gas is selected from a group consisting of:

a. chlorine b. nitrogen c. air, and d. carbon monoxide. 5. A method in accordance with claim 1, including blowing said carrier gas a rate less than 830 cubic feet per hour per ton of input melt. 6. A method in accordance with claim 1, including blowing said carrier gas in an amount less than 830 cubic feet per ton. 7. A method in accordance with claim 1, wherein said impurity content is present in said input melt in an amount in a range of 0.10% to 1.40% by weight of the melt. 8. A method in accordance with claim 1, including continuing said gaseous blow until the impurity content is equal to or less than 0.006% by weight. 9. A method in accordance with claim 1, wherein said temperature is within the range between approximately 2500 F and approximately 2800 F. 10. A method in accordance the claim. 1, including blowing said gas for a period between approximately 45 minutes and approximately 1 hour.

9 10 11. A method in accordance with claim 1, wherein a lead impurity content in excess of 0.10% by weight said input melt material includes a manganese conof the melt.

tent in the range from approximately 60% by 12. A method in accordance with claim 1, including weight to approximately 2% by weight, maintaining the temperature of said input melt below a silicon content in the range for approximately 2.4% the boiling temperature of said impurity content.

by weight to approximately 30% by weight, and 

1. A METHOD FOR PRODUCING FERRO-ALLOYS FROM A MANGANESE CONTAINING ORE FOR USE IN STEEL PRODUCTION, THE STEPS COMPRISING, PROVIDING AN INPUT MELT FROM MANGANESE CONTAINING ORE WITH SAID INPUT MELT COMPRISING A MANGANESE-CONTAINING MATERIAL SELECTED FROM A GROUP CONSISTING OF: A. A SILICO-MANGANESE FERRO-ALLOYS, B. A MANGANESE-SILICON FERRO-ALLOY, C. A LOW CARBON FERRO-MANGANESE, AND D. A MASSIVE MANGANESE, SAID INPUT MELT CONTAINING A MOLTEN IMPURITY CONTENT SELECTED FROM THE GROUP CONSISTING OF: A. LEAD, B. ARSENIC, AND C. ZINC PROVIDING THE IMPURITY CONTENT IN AN AMOUNT IN EXCESS OF 0.01 BY WEIGHT, PROVIDING A CARRIER GAS OF THE TYPE WHICH DOES NOT GENERALLY REACT OR COMBINE WITH THE MATERIALS OF SAID INPUT MELT OR SAID IMPURITY CONTENT AT A TEMPERATURE ABOVE THE MELTING TEMPERATURE OF SAID IMPURITY CONTENT, BUT BELOW THE VAPORIZATION TEMPERATURE THEREOF, BLOWING SAID CARRIER GAS ENTIRELY THROUGH SAID INPUT MELT SO THAT IT WILL PASS OUT OF THE INPUT MELT, MAINTAINING THE TEMPERATURE OF SAID INPUT MELT ABOVE THE MELTING TEMPERATURE OF SAID IMPURITY CONTENT WHILE BLOWING SAID CARRIER GAS THERETHROUGH AND, SEPARATING SAID IMPURITY CONTENT FROM SAID INPUT MELY BY SAID CARRIER GAS TO CAUSE SAID IMPURITY CONTENT TO BE EVAPORATED AND REMOVED AS A GASEOUS VAPOR IN SUBSTANTIALLY ITS ELEMENTAL STATE ALONG WITH SAID CARRIER GAS AS IT PASSES OUT OF SAID INPUT MELT TO REDUCE THE IMPURITY CONTENT IN SAID MELT TO AN AMOUNT LESS THAN 0.01% BY WEIGHT.
 2. A method in accordance with claim 1, including blowing a carrier gas of the type having a minor percentage by weight of free oxygen.
 3. A method in accordance with claim 1, including blowing a carrier gas having less then 22% by volume or 24% by weight of free oxygen.
 4. A method in accordance with claim 1, wherein said carrier gas is selected from a group consisting of: a. chlorine b. nitrogen c. air, and d. carbon monoxide.
 5. A method in accordance with claim 1, including blowing said carrier gas a rate less than 830 cubic feet per hour per ton of input melt.
 6. A method in accordance with claim 1, including blowing said carrier gas in an amount less than 830 cubic feet per ton.
 7. A method in accordance with claim 1, wherein said impurity content is present in said input melt in an amount in a range of 0.10% to 1.40% by weight of the melt.
 8. A method in accordance with claim 1, including continuing said gaseous blow until the impurity content is equal to or less than 0.006% by weight.
 9. A method in accordance with claim 1, wherein said temperature is within the range between approximately 2500* F and approximately 2800* F.
 10. A method in accordance the claim 1, including blowing said gas for a period between approximately 45 minutes and approximately 1 hour.
 11. A method in accordance with claim 1, wherein said input melt material includes a manganese content in the range from approximately 60% by weight to approximately 2% by weight, a silicon content in the range for approximately 2.4% by weight to approximately 30% by weight, and a lead impurity content in excess of 0.10% by weight of the melt.
 12. A method in accordance with claim 1, including maintaining the temperature of said input melt below the boiling temperature of said impurity content. 